Abstract

Numerous pathological amyloid proteins spread from cell to cell during neurodegenerative disease, facilitating the propagation of cellular pathology and disease progression. Understanding the mechanism by which disease-associated amyloid protein assemblies enter target cells and induce cellular dysfunction is, therefore, key to understanding the progressive nature of such neurodegenerative diseases. In this study, we utilized an imaging-based assay to monitor the ability of disease-associated amyloid assemblies to rupture intracellular vesicles following endocytosis. We observe that the ability to induce vesicle rupture is a common feature of α-synuclein (α-syn) assemblies, as assemblies derived from WT or familial disease-associated mutant α-syn all exhibited the ability to induce vesicle rupture. Similarly, different conformational strains of WT α-syn assemblies, but not monomeric or oligomeric forms, efficiently induced vesicle rupture following endocytosis. The ability to induce vesicle rupture was not specific to α-syn, as amyloid assemblies of tau and huntingtin Exon1 with pathologic polyglutamine repeats also exhibited the ability to induce vesicle rupture. We also observe that vesicles ruptured by α-syn are positive for the autophagic marker LC3 and can accumulate and fuse into large, intracellular structures resembling Lewy bodies in vitro. Finally, we show that the same markers of vesicle rupture surround Lewy bodies in brain sections from PD patients. These data underscore the importance of this conserved endocytic vesicle rupture event as a damaging mechanism of cellular invasion by amyloid assemblies of multiple neurodegenerative disease-associated proteins, and suggest that proteinaceous inclusions such as Lewy bodies form as a consequence of continued fusion of autophagic vesicles in cells unable to degrade ruptured vesicles and their amyloid contents.

Notes

Acknowledgements

The authors wish to acknowledge Michael Sobieraj for assistance with construct generation and protein purification, Oksana I. Zhurbich for assistance with electron microscopy, and Sean C. Liebscher for assistance with assembly characterization, as well as all laboratory members for discussion. EMC was funded by the Michael J. Fox foundation, RRI award. JHK was funded in part by a Center Grant from the Parkinson’s disease Foundation. RM and LB were funded by Grants from the Agence Nationale de la Recherche (ANR-14-CE13-0031) and the EC Joint Programme on Neurodegenerative Diseases (JPND-NeuTARGETs-ANR-14-JPCD-0002-02; JPND-SYNACTION-ANR-15-JPWG-0012-03), the Centre National de la Recherche Scientifique, France Parkinson (Contract 113344), the Fondation de France (Contract 2015-00060936), The Fondation pour la Recherche Médicale (Contract DEQ 20160334896), a “Coup d’Elan a la Recherche Francaise” award from Fondation Bettencourt-Schueller and the Fondation Simone et Cino Del Duca of the Institut de France. WPF was supported by the Illinois Chapter of the ARCS Foundation, the Arthur J. Schmitt Foundation, and a fund from the Dean of the Stritch School of Medicine.